A new generation of optoelectronic devices such as organic thin film transistors (TFT), organic light emitting diodes (OLEDs), printable circuits, organic photovoltaic devices, capacitors and sensors are built upon organic semiconductors as their active components. These devices need to achieve performance compatible with their envisioned applications such as display backplanes, radio-frequency identification tags, printed sensors and photovoltaics. Like inorganic material-based electronics, organic semiconductor-based devices can operate efficiently and at high speed if both p-type and n-type semiconductor materials exhibit high charge carrier mobility and stability under ambient conditions, and can be processed in a cost-effective manner.
The most promising organic semiconductors include π-conjugated small molecules and polymers that have an electronic structure compatible with efficient charge transport and suitable for charge injection from the electrical contacts. To date, most of the organic semiconductors that have been investigated and optimized are p-type semiconductor materials due to their enhanced environmental stability. In contrast, n-type semiconductors are limited to a small number of molecules and polymers, most of which are inactive under ambient conditions. It has been reported that some core-cyanated rylenes, including perylenes, anthracenes, naphthalenes, and the like, can be active under ambient-conditions and can exhibit processing versatility. See e.g., Tang, C. W. (1986), Appl. Phys. Lett., 48: 183; Law, K. Y. (1993), Chem. Rev., 93: 449; and Forrest, R. F. (1997), Chem. Rev., 97: 1793.
While both contact and noncontact printing techniques have been employed for the fabrication of electronic devices, wider application of organic semiconductor materials in printable circuits has been constrained by the unavailability of suitable formulations. For example, satisfactory printing results only can be obtained if these materials can be formulated in printing medium with appropriate viscosity. In some instances, inclusion of binders is not a feasible option because of their negative impact on the carrier mobility of the semiconductor materials.
Accordingly, the art desires new n-type organic semiconductor materials, especially those that can be formulated in solutions of a broad viscosity range suitable for use in various solution processing techniques including, but not limited to, contact and noncontact printing.